UEFA has charged Manchester City in relation to fireworks being set off during their Champions League quarter-final victory over Paris Saint-Germain on Tuesday.
Kevin De Bruyne scored the only goal during the Etihad Stadium leg, securing a 3-2 aggregate win for Manuel Pellegrini's side.
Following De Bruyne's goal a blue flare was visibly let off in the ground's south stand.
A statement released by UEFA read: "Disciplinary proceedings have been opened following the UEFA Champions League second-leg quarter final between Manchester City FC and Paris Saint-Germain (1-0) played on 13 April in England.
"Charges against Manchester City FC: Setting off of fireworks - Art. 16 (2) of the UEFA Disciplinary Regulations."
City's case will be dealt with by the UEFA Control, Ethics and Disciplinary Body on May 19 and it is not the first time that fan behaviour at a Champions League match this season has left them at odds with European football's governing body.
Following October's 2-1 victory over Sevilla, City were charged in relation to their fans booing pre-match Champions League anthem although UEFA eventually decided against taking any action.
The booing, a protest by fans relating to the club's 2013 punishment under financial fair play regulations and the presence of CSKA Moscow followers at a 2014 match against City that officially took place behind closed doors due to racism offences by the Russian team's supporters, has continued unabated and was particularly loud ahead of the PSG match.